1. Field of Invention
Apparatuses and methods consistent with the present invention relate to a back light apparatus and a control method thereof, and more particularly, to a back light apparatus which uses light emitting diodes (LEDs) of various colors as a light source, and a control method thereof
2. Description of the Related Art
In the related art back light apparatus using an LED as a light source, a red LED (R LED), a green LED (G LED) and a blue LED (B LED) respectively have different lighting efficiencies. Accordingly, currents to be supplied to the LEDs for respective colors are different from one another. Also, the LEDs for different colors are receive different voltages and consume different power because they are different from one another in semiconductor composition.
The back light apparatus using the R LED, the G LED and the B LED as a light source optically mixes lights of different colors to generate predetermined chromaticity corresponding to a white light. For this, the back light apparatus detects the amount of the lights of the respective colors by a red light sensor, a green light sensor and a blue light sensor, and adjusts the currents supplied to the respective LEDs based on feedback control. Accordingly, the back light apparatus adjusts the predetermined chromaticity to the white light by mixing the red light, the green light and the blue light.
The related art back light apparatus having the LEDs as the light source previously calculates the initial amounts of the currents (for example, Pulse Width Modulation (PWM) duty rate) of the respective red light, green light and blue light, and drives the LEDs of respective colors based on the initial amounts of the currents just after power is supplied to the related art back light apparatus.
However, the lighting efficiency decreases if time is passed. Thus, though the currents having maximum values are supplied to the respective R LED, G LED and B LED, the respective LEDs may not present corresponding brightness. Accordingly, the back light apparatus cannot control the LEDs based on the brightness generated by the current having the maximum value. In other words, if the back light apparatus controls the brightness of the LED based on the output of the LED, the brightness is not correctly adjusted because the output is changed depending on deterioration of the LED.
Also, if the brightness of the light source should be controlled per frame unit, it is not desirable to control the brightness while changing an output reference of the sensor per the frame unit, and it is practically difficult to be controlled by this method.